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At least 1,387 records · Page 77Linked to original sources

PubMed2002

Inhibition of growth of human breast cancer cells in culture by neutron capture using liposomes containing 10B.

Cell destruction in boron neutron capture therapy is effected by nuclear reaction between 10B and thermal neutrons with the release of alpha-particles (4He) and lithium-7 ions (7Li). 4He kills cells within 10 microm of the site of 4He generation, therefore it is theoretically possible to destroy tumour cells without affecting adjacent healthy tissue, given selective delivery of compounds containing 10B. Liposomes wore prepared by vortex dispersion of solutions containing 10B compounds with dried lipid films and the effects of those compounds on human breast cancer cells in culture were examined after thermal neutral irradiation. [3H]-TdR incorporation by MRKnu/nu-1 cells treated with 10B-containing liposomes showed 40% suppression compared with liposomes without 10B, at 2 x 1012 n/cm2 thermal neutron fluence. Inhibition of tumour cell growth with liposomes prepared with 100 mm 10B-compound was as significant as with those made with 500 ppm 10B solution. The concentration of 10B in liposomes was 76.5 +/- 3.4 microg/mL. Boronated liposomes can thus deliver sufficient 10B atoms to this line of breast cancer cells in culture to effect cytotoxicity and suppression of growth after thermal neutron irradiation.

Boron↗

PubMed2001

Pediatric neuroanesthesia. Arteriovenous malformations.

Intracranial arteriovenous malformations can occur singly, multiply, and in conjunction with aneurysms and denovo, family, or in conjunction with connective-tissue disorders. Intracranial hemorrhage is the most common presentation, occurring in 20% to 50% of cases. In children, seizures are the second most common presentation occurring in 15% to 20% of cases. The modalities available treatment of arteriovenous malformations are microsurgery, embolization, and stereotactic radiosurgery with heavy particles, alpha knife, or linear accelerator. Induction, maintenance, and emergence from anesthesia are designed to prevent rupture of arteriovenous malformation and aneurysm and to improve intracranial compliance in the presence of an intracranial hematoma, during both diagnostic (CT, MR scanning) and therapeutic procedures.

Anesthesia↗

PubMed2001

Production, concentration and deep purification of 111In radiochemicals.

A new method of 111In separation from a silver target irradiated with 30 MeV alpha-particles is described. The 111In isolation from Ag and Cd is based on its co-precipitation with La(OH)3. The 111In separation from La(III) has been performed by the method of ion-exchange chromatography. A multi-stage purification technique was developed that allows the production of 111In radiochemicals in which the part of impurities of di-, tri-valent metal atoms is negligible.

Journal Article↗

PubMed2001

Breakthrough of 225Ac and its radionuclide daughters from an 225Ac/213Bi generator: development of new methods, quantitative characterization, and implications for clinical use.

Bisumth-213, a short-lived alpha particle emitting radionuclide, is generated from the decay of 225Ac, which has a half-life of 10 days. The development of a clinical 225Ac/213Bi generator and the preparation of a 213Bi radiolabeled antibody for radioimmunotherapy of leukemia have been reported. The 225Ac decay scheme is complex; therefore a thorough understanding of the impact of both the parent 225Ac and its daughters on radiolabeling, purification, and quantification is necessary for optimal use of the generator system. This paper reports: (i) unique new methods to measure 221Fr, 213Bi, and 209Pb, the prominent daughters of 225Ac; and (ii) a quantitative evaluation of 225Ac/213Bi generator breakthrough and the radionuclidic purity of 213Bi labeled radiopharmaceutical dose formulations. A quantitative multi-dimensional proportional scanning method was employed to distinguish and measure specific daughter radionuclides. This method combines thin layer chromatography in two perpendicular directions with attenuated collimation as a function of time for data collection and analysis. Francium-221 and 213Bi eluted differentially from the generator, and 221Fr contributed minimally to unchelated 213Bi in the reaction and final products. Lead-209 was present in the reaction solution, but not strongly bound by the chelating moiety either (i) under the 213Bi labeling reaction conditions or (ii) following chelated 213Bi decay. As a consequence of incorporating several new procedures to the operation of the generator, 225Ac breakthrough in the final product was further reduced and represented a trivial contaminant in the final drug formulations.

Actinium↗

PubMedDate not supplied

A source for measurement of the absolute intensities of 226Ra gamma-radiation in equilibrium with decay products.

The design and production techniques of a gamma-ray spectrometric source of 226Ra in equilibrium with its daughter decay products have been developed. The radon emanation coefficient of the source did not exceed 0.1%. The 226Ra activity in the gamma-ray spectrometric source was measured relative to that in an alpha-particle spectrometric source by comparison of the intensities of the main gamma rays using a semiconductor gamma-ray spectrometer. The total uncertainty of the activity measurement results was 0.5% for a coverage factor of k = 2.

Journal Article↗

PubMed2002

Characterization of the Oum Er Rbia (Morocco) high basin karstic water sources by using solid state nuclear track detectors and radon as a natural tracer.

Uranium and thorium contents as well as radon alpha-activities per unit volume were evaluated inside different water samples by using a method based on calculating the CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs) detection efficiencies for the emitted alpha-particles and measuring the resulting track density rates. The validity of the SSNTD technique utilized was checked by analysing uranyl nitrate (UO2(NO3)26H2O) standard solutions. A relationship between water radon concentration and water transmission of different water sources belonging to two regions of the Middle Atlas (Morocco) water reservoir was found. The influence of the water flow rate as well as the permeability and fracture system of the host rocks of the sources studied was investigated.

Morocco↗

PubMed2002

Use of three new SSNTD methods for evaluating thorium contents in different building materials and measuring thoron and its progeny concentrations inside dwellings.

Three new methods based on using CR-39 and LR- 115 type II solid state nuclear track detectors (SSNTD) were used for measuring thorium concentrations (in 10(-6)g/g (ppm)) inside different building materials and evaluating the resulting concentrations of thoron and its progenies in dwellings built by the studied materials. The first technique consists of determining the probabilities for alpha-particles emitted by the uranium and thorium series inside the building materials or by the radon and thoron groups inside the dwelling atmosphere to reach and be registered as tracks on the SSNTD utilized and exploiting the resulting track density rates. The second method consists of evaluating the mean critical angles of etching of the CR-39 and LR-115 II SSNTD and measuring the resulting track densities registered on the detectors utilized. The third technique is based on calculating the detection efficiencies of the CR-39 and LR-115 II SSNTD for a-particles emitted by the uranium and thorium series in the building materials or by the radon and thoron groups in air and measuring track density rates registered on these detectors. The influence of the building material's nature and ventilation rate on the thoron and its decay products inside the dwelling rooms studied has been investigated.

Journal Article↗

PubMed2000

Evaluation of the contribution of smoking to total blood polonium-210 in Saudi population.

A preliminary study of 210Po concentrations in the blood of some smokers and nonsmokers is presented in order to evaluate the contribution of smoking to total blood 210Po in Saudi population. Blood samples were collected from 30 volunteers and analyzed by high resolution alpha-spectrometry using a radiochemical technique. The technique is based on the separation of polonium from other components of the sample by wet ashing with an HNO3/H2O2 oxidizing mixture and spontaneous deposition on a silver disc under the relevant conditions for alpha-particle counting. The results indicated that a significant fraction (about 30%) of blood 210Po is related to smoking.

Adolescent↗

PubMed2000

Standardization and photon emission probabilities in the decay of 237Np/233Pa

The activity concentration of a 237Np solution was determined by 4pialpha counting, by alpha particle spectroscopy with defined solid angle and by liquid scintillation counting (LSC). These methods yielded results which differ by less than 0.1% from the mean, the relative standard uncertainties being 0.23% (4pialpha), 0.27% (LSC) and 0.5% (solid angle). X-ray and gamma-ray emission probabilities of several transitions were measured using semiconductor detectors.

Journal Article↗

PubMed2000

Improvements in quantitative source preparation

Quantitative source preparation is indispensable for radionuclide standardisation. To improve the source quality, a device has been developed to accelerate the evaporation of solvents from a drop deposited on a substrate. Short drying times were reached by stirring the rotating drop with multiple jets of dry nitrogen at elevated temperature. Uniform deposits with a large number of small crystals were obtained. The source-quality was checked by micrographs and scans of autoradiographs and by the shape parameters of alpha-particle spectra.

Journal Article↗

PubMed2000

On the determination of activity profiles in wide-area reference sources

A method is described for determining the depth distribution of the radioactive substance of alpha-emitting nuclides in a wide-area reference source. The method combines measurements and calculations. In the experimental part, the energy spectrum of the source is measured by means of an alpha spectrometer. The energy spectrum is then modelled by the Monte Carlo method, taking into account energy loss of alpha particles in the source matrix, energy-loss straggling and the parameters of the spectrometer. Additional parameters for the characterization of reference sources are derived from the integral of the depth distribution. The investigations prove that the production process of commercial sources can be controlled in such a way that more than 90% of the radioactive material is implanted in the top layer of 5 microm thickness of an aluminum foil.

Journal Article↗

PubMed2000

Application of alpha/beta discrimination in liquid scintillation counting for the purity control of 99mTc medical solutions.

99mTc is a widely used nuclide in nuclear medicine for diagnosis. 99mTc solutions are eluted from 99Mo/99mTc generators as sodium chloride solutions. As the 99Mo source is a fission product extracted from the reprocessing of nuclear fuel, one might expect the presence of radioactive impurities. One point of special concern described in the 1997 European Pharmacopoeia (1996) is the possible contamination in alpha-impurities (U, Pu, Am, Cm, ...) which must be very low. In order to check this impurity concentration, we used liquid scintillation counting (LSC) with alpha/beta discrimination and a commercial extractive scintillator, Alphaex. We first made measurements using synthetic mixtures of alpha and beta-emitters and then using the real effluent. This paper describes the measurement procedure used with the optimum chemical conditions for a correct extraction of the alpha-emitting nuclides. The sensitivity of the method is also described from the measurements made using the real effluent with an addition of a quantitative amount of alpha particle contamination.

Biological Science Disciplines↗

PubMed2001

Synthesis, purification and biodistribution of (205)Bi-DOTMP, visualizing bone deposition patterns with autoradiography.

A HPLC system has been developed for carrier free and rapid delivery in a physiological buffer of the alpha-particle emitting bone-seeking radiopharmaceutical (212)Bi-DOTMP. (205)Bi-DOTMP was synthesized and HPLC purified to mimic and visualize the deposition pattern in bony tissues of (212)Bi-DOTMP by autoradiography. Inhomogeneous bone deposits were found with the highest concentration in the bone matrix, the endosteum and in the growth zones of young mice. Analysis of urine samples showed that (205)Bi-DOTMP was cleared as an intact complex.

Animals↗

PubMed2002

Sodium-iodide symporter (NIS)-mediated accumulation of [(211)At]astatide in NIS-transfected human cancer cells.

The cellular expression of the sodium iodide symporter (NIS) has been shown to confer iodide-concentrating capacity in non-thyroid cell types. We examined the role of NIS in the uptake of the alpha-particle emitting radiohalide [(211)At]astatide in the UVW human glioma cell line transfected to express NIS. [(211)At]Astatide uptake is shown to be NIS-dependent, with characteristics similar to [(131)I]iodide uptake. These studies suggest [(211)At]astatide as a possible alternative radionuclide to [(131)I]iodide for NIS-based endoradiotherapy, and provide a model for the study of [(211)At]astatide behavior at a cellular level.

Astatine↗

PubMed2003

Experimental therapy of disseminated B-Cell lymphoma xenografts with 213Bi-labeled anti-CD74.

A (213)Bi-labeled antibody to CD74 was evaluated as a therapeutic agent for B-cell lymphoma. The alpha-particle emission, with a half-life of 46 min, is appropriate for therapy of micrometastases. The labeled Ab retained full immunoreactivity, and was potent at single-cell kill of the Raji B-lymphoma cell line. Approximately 30 decays of cell-bound (213)Bi was required for a cell kill of 99%, and dosimetry calculations suggested that the cGy dose delivered was sufficient to produce the level of toxicity observed. A non-reactive control Ab, labeled similarly, also produced toxicity, due to decays occurring in the medium, but was approximately 3-fold less potent than the reactive Ab. In a SCID mouse xenograft micrometastatic model, Ab injection at day 2 or day 5 after tumor inoculation resulted in strong, specific suppression of tumor growth, with some apparent cures.

Animals↗

PubMed1998

Preparation of 211At-labeled humanized anti-Tac using 211At produced in disposable internal and external bismuth targets.

These studies describe the production and purification of 211At as well as the procedure for labeling humanized anti-Tac, the antibody to the alpha-chain of the IL-2 receptor (IL-2R alpha), which has been shown to be a useful target for immunotherapy. The optimized protocol combines the advantages of the two-stage dry distillation procedure with the astatination of trialkylstannyl substances as labeling compounds for proteins. The 211At was produced by bombarding either an external or a recently developed disposable internal bismuth target with alpha-particles from a Cyclotron Corporation CS-30 cyclotron. The 211At was found to contain less than 0.01% 210At. The production rate for the external target was 0.15 mCi +/- 0.056 microA(-1) h(-1) (n = 9) (5.55 MBq mcroA[-1] h[-1]). The production rate for the internal target was 0.44 +/- 0.14 mCi microA(-1) h(-1) (n = 16) (16.28 MBq mcroA[-1] h[-1]).

Astatine↗

PubMed2000

Synthesis, characterization, and evaluation of a novel bifunctional chelating agent for the lead isotopes 203Pb and 212Pb.

Radioisotopes of Pb(II) have been of some interest in radioimmunotherapy and radioimmunoimaging (RII). However, the absence of a kinetically stable bifunctional chelating agent for Pb(II) has hampered its use for these applications. 203Pb (T(1/2) = 52.02 h) has application potential in RII, with a gamma-emission that is ideal for single photon emission computerized tomography, whereas 212Pb (T(1/2) = 10 h) is a source of highly cytotoxic alpha-particles via its decay to its 212Bi (T(1/2) = 60 min) daughter. The synthesis of the novel bifunctional chelating agent 2-(4-isothiocyanotobenzyl)-1,4,7,10-tetraaza-1,4,7,10-tetra- (2-carbamoyl methyl)-cyclododecane (4-NCS-Bz-TCMC) is reported herein. The Pb[TCMC]2+ complex was less labile to metal ion release than Pb[DOTA]2- at pH 3.5 and below in isotopic exchange experiments. In addition to increased stability to Pb2+ ion release at low pH, the bifunctional TCMC ligand was found to have many other advantages over the bifunctional 1,4,7,10-tetraazacyclodocane-1,4,7,10-tetraacetic acid (DOTA) ligand. These include a shorter and more straightforward synthetic route, a more efficient conjugation reaction to a monoclonal antibody (mAb), with a higher chelate to protein ratio, a higher percent immuroreactivity, and a more efficient radiolabeling reaction of the mAb-ligand conjugate with 203Pb.

Chelating Agents↗

PubMed2000

Advances in the use of monoclonal antibodies in cancer radiotherapy.

The use of monoclonal antibodies (MAbs) as radiation carriers in argeted radiotherapy of cancers has produced striking clinical responses in hematologic diseases, such as non-Hodgkin's lymphoma. Novel strategies are currently being examined in an effort to improve efficacy in solid tumor therapies. Two of these strategies involve minimizing the systemic toxicity of a circulating radionuclide via 'pretargeting', and the sensitization of tumors to radiation by combination therapy with radiosensitizing drugs. Advances made in radiolabeling chemistries and in the use of alpha-particle emitters can also improve utility. Clinical evidence suggests that radioimmunotherapy may be best applied in minimal-disease and adjuvant settings in combination with other cancer therapy modalities.

Journal Article↗